Hapten radioimmunoassay is known to be useful for the measurement of small components in the living body, especially steroid hormones. However, there are very few reports in the literature concerning the assay of such a small molecules as catecholamines.
Went et al reported that adrenaline antigen was prepared by coupling diazoadrenaline with a serum albumin under at alkaline conditions. Since catecholamines are unstable under alkaline condition in the presence of oxygen, the antigen may be structurally changed at the catechol portion, so the antibodies produced therefrom may not be specific for adrenaline (Arch. Exp. Path. Pharm. 193 page 609 (1939)).
Spector disclosed the synthesis of catecholamine antigens by conjugating a catecholamine with a protein or polypeptide in the presence of a carbodiimide by a peptide linkage (U.S. Pat. No. 3,704,282). While the amino group of the catecholamine is utilized in the peptide linkage, such amino group of the catecholamine should be maintained as free form in the conjugate for the production of the specific antibody.
Therefore, these antigens previously reported are not satisfactory for the production of the specific catecholamine antibodies.